백준 1260번(Java)

import java.io.*;
import java.util.*;

public class Main {

	static StringBuilder sb = new StringBuilder();
	static boolean[] check;
	static int[][] arr;

	static int node, line, start;

	static Queue<Integer> q = new LinkedList<>();

	public static void main(String[] args) throws IOException {

		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		StringTokenizer st = new StringTokenizer(br.readLine());
		node = Integer.parseInt(st.nextToken());
		line = Integer.parseInt(st.nextToken());
		start = Integer.parseInt(st.nextToken());

		arr = new int[node + 1][node + 1];
		check = new boolean[node + 1];

		for (int i = 0; i < line; i++) {
			StringTokenizer str = new StringTokenizer(br.readLine());

			int a = Integer.parseInt(str.nextToken());
			int b = Integer.parseInt(str.nextToken());

			arr[a][b] = arr[b][a] = 1;
		}
		dfs(start);
		sb.append("\n");
		check = new boolean[node + 1];

		bfs(start);

		System.out.println(sb);

	}

	public static void dfs(int start) {

		check[start] = true;
		sb.append(start + " ");

		for (int i = 0; i <= node; i++) {
			if (arr[start][i] == 1 && !check[i])
				dfs(i);
		}

	}

	public static void bfs(int start) {
		q.add(start);
		check[start] = true;

		while (!q.isEmpty()) {

			start = q.poll();
			sb.append(start + " ");

			for (int i = 1; i <= node; i++) {
				if (arr[start][i] == 1 && !check[i]) {
					q.add(i);
					check[i] = true;
				}
			}
		}

	}

}